DescriptionFe95PdH5 and Fe95Pd5 nanopowders were prepared by mechanical alloying (MA) using high energy ball milling. Two ways of the sample preparation were compared in order to examine the effect of hydrogen on MA: (i) A-sample: Pd powder was pre-charged with hydrogen and subsequent MA of Fe and PdH was performed in Ar protective atmosphere; (ii) B-sample: Fe and Pd powders were mechanically alloyed in hydrogen atmosphere. The milling procedure was interrupted and alloying followed by several experimental methods up to the final state achieved after 50 h of milling.